Yogurt Incubation Temperature

[Guest guest]

I've been using a very inexpensive yogurt maker that has been working well and

keeps the temperature at a pretty consistent 110 F. My sister just got the same

machine on my recommendation but hers goes to 120 F.

I thought I had seen somewhere on the internet that yogurt bacteria starts to

die at above 120 so I decided to do a little more research.

Temperatures were all over the place going up as high as 130 F. I found a

tutorial by a professor of Chemistry and Biology at a university in Ohio on how

to make yogurt. He uses Dannon All Natural Plain Yogurt as starter.

http://biology.clc.uc.edu/fankhauser/Cheese/yogurt_making/YOGURT2000.htm

This is an excerpt from the web page on temperature:

b. proper incubation temperature. Lactobacilli and Streptococcus thermophilus

are thermophilic bacteria, meaning they prefer elevated temperatures for growth.

At such temperatures (50 C, in this case) pathogenic or putrifactive bacteria

are inhibited. However, even these thermophilic bacteria are killed if exposed

to temperatures over 55oC (130o F), and do not grow well below 37oC (98oF). We

will incubate at 50oC, a temperature on the high side of its preferred growth

temperature (122oF), a temperature which inhibits the growth of pathogenic

bacteria. (Note that many recipes call for cooler temperatures than this. We

find the results less dependable when incubation temperatures are lower.)

I checked the university website to make sure sure this guy was truly a

professor and emailed him. I thought the reason Elaine gave us the temperature

range of 98-110 is because we incubate our yogurt for so long. I asked the

professor about that and this was his reply:

" Incubating at the temp I specify does not kill yogurt bacteria because they are

`thermophilic " which means they LIKE heat. Yes, you CAN incubate too hot, but

122 is within their rang. Incubating longer will digest more of the lactose,

and make it more sour. "

So, according to this guy our yogurt is OK as long as it doesn't go above 130 F.

This would be mean no more dimmers for some of you!

Any thoughts on this?

On a related topic...

I use Dannon All Natural Plain Yogurt as starter. On the container it says:

" Contains active yogurt cultures including L. Acidophilus " .

I was curious as to what the other cultures were, emailed Dannon, and this is

what they emailed back:

" All Dannon products contain the two required cultures (Streptococcus

thermophilus and Lactobacillus bulgaricus). Most of our yogurts contain a third

culture, which is not required, Lactobacillus acidophilus. Dannon Activia

contains the culture Bifidus Regularis. Dannon DanActive contains the culture

L. casei Immunitas. Danimals Drinkables contain Lactobacillus GG or LGG. At

the current time, Dannon does not add any other cultures to our products. "

V.